The way I find the files are by searching under my downloads folder and then I search by date. Where your downloads go are entirely dependent on how you have set up your own directory on your computer. There is usually a “Downloads” file in your folders. You can then open (upload) the downloaded file in Google sheets and make any changes necessary.
I do not know what type of computer or version, if it is Microsoft based or a MAC, on my computer it is always on the side menu. Sometimes you can see it appear briefly on the bottom of your screen.